8

mental ray Volume Shading 93
Same scene with global illumination
Global illumination ma de smoother by final gather
To calculate global illumination, the mental ray
renderer uses the
photon map technique (page
3–1088)
.
Impor tant: The mental ray renderer generates global
illumination without requiring you to generate a
radiosity solution. A photon map is a model of global
illumination in its own ri ght.
Using a photon map can cause rendering artifacts
such as dark corners and low-frequency variations
in the lighting. You can reduce or eliminate these
art ifac ts by tur ning on
final gathering (page
3–1034)
, which increases the number of rays used
to calculate global illumination.
You enable global illumination and final gathering
on the Render Scene dialog > Indirect Illumination
panel >
Caustics And Global Illumination rollout
(page 3–104)
.Inaddition,youmustdesignate:
• Which light objects can generate global
illuminat ion.
• Which renderable objects can generate global
illuminat ion.
• Which renderable objects can receive global
illuminat ion.
The settings for generating and receiving global
illumination are on the Object Properties dialog >
mental ray Panel (page 1–121) .
mental ray Vol ume S hading
Volume shading shades a three-dimensional
volume, rather than a surface. Typically , volume
shaders provide atmospheric effects such as mist
and fog.
Model rendered with no volume effect